Transducers, and in particular ultrasonic transducers, are utilized in many applications, such as medical imaging, where high precision is required. Particularly when the transducers are being used for medical imaging, an error in the positioning of the transducer when readings are being taken could lead to a false diagnosis or treatment. FDA regulations also limit the acoustic power output which may be utilized for imaging various areas of the body and various classes of patient such as fetal or infant. Precise control of power output is therefore required, particularly for transducers which are to be used for more than one class of imaging.
Heretofore, control of transducer position to a selected level of precision has been achieved by maintaining high tolerances in the manufacturing process and by carefully testing and hand-adjusting transducer units which do not conform to these tolerances. For example, mechanical scanning transducers typically have a position sensor, the output from which is compared with a reference signal, and the error output from the comparator is utilized to control a servo-motor which moves the transducer through its scan path. Any nonlinearity in the position sensing device can result in false position readings and can also cause slight variations in the sweep speed of the transducer. Even when great care and expense are taken in the manufacturing process and in the hand adjustment of the device, it is impossible to eliminate all nonlinearity from the position sensing mechanism. As a result, such transducers have been relatively expensive while still providing less than ideal operation.
Similarly, the power output characteristics of individual transducer elements may vary slightly with the applied input, making it difficult, even with high manufacturing tolerances, to provide transducers which produce required acoustic power outputs for different classes of service. Again, even at relatively high cost, less than ideal results are achieved.
Since, either because of FDA regulations, or for other reasons, certain transducers may not be suitable for certain classes of service, it would be desirable if a means could be provided to inhibit the use of such transducers for such classes of service. Existing transducers do not generally provide such a capability.
Another problem with existing transducers is that each transducer has various constants and other parameter values which must be known to the system utilizing the transducer in order for the system to properly control the transducer and to properly interpret the results obtained therefrom. Heretofore, the system utilizing the transducer has had to store representative values for each class of transducer which might be utilized with the system and select the appropriate values from an identification of the class of transducer being used with the system at any given time. This information as to the class of transducer being used may either be inputted manually or may be read from a simple data storage element included with the transducer.
This procedure suffers from a number of limitations. First, while the various constants and other values which are stored are substantially uniform for a given class of transducer, there may be substantial variations in these values among individual transducers in the class. Thus, while the stored values may be usable for all transducers of a class, they are not the exact values for the particular transducer being utilized at any given time. Differences between the average stored values and the actual values for the transducer being utilized may result in erroneous outputs in some applications.
Further, over the years that an ultrasonic system is utilized, new classes of transducers will become available, the parameters for which are not initially stored in the system. This necessitates a reprogramming of the system which includes either firmware or software changes for each new transducer or family of transducers which are provided for use with the system. Software media and/or documentation must therefore be provided with each new release of transducer to permit appropriate updating of the systems in which the transducers may be utilized.
Another potential problem with existing transducers is that, to the extent there are any records at all on use of a transducer, such records are normally manually maintained. Since the transducer used in a given system may be varied for varying applications, it may be difficult or impossible to determine the period that a given transducer has actually been used. Thus, there is normally no record of the actual number of hours of use for a given transducer. Such information could be useful in determining when a transducer should be replaced, when preventive maintenance should be performed, or for other service or related purposes. Such information would also permit service histories on transducers or classes of transducers to be developed which could be used for various purposes.
Finally, no current mechanism exists for informing the ultrasonic or other transducer system on the full range of operating parameters for a given transducer, such as its type, model number, serial number, and various advertised and actual characteristics such as frequency, maximum scan angle, focal distance and the like.
It is therefore an object of this invention to provide a relatively simple and inexpensive mechanism for use in transducer systems for assuring positional accuracy, uniform scan rate and proper power output from the transducer element while at the same time reducing manufacturing tolerances for the transducer.
A more specific object of this invention is to provide an ultrasonic transducer system which is capable of compensating for nonlinearity in the position sensing mechanism so as to permit accurate positioning of the transducer element and a uniform scan rate for the element.
Another object of this invention is to provide a mechanism for providing to a transducer system accurate information concerning the operating characteristics and constants of the transducer being utilized in the system without requiring any reprogramming of the system.
Still another object of this invention is to provide a simple mechanism for keeping track of such things as the age of a transducer element, the actual period of use for the transducer, the period of use for various classes of service, the period of use since last maintenance, and the like.